Process for recovering diolefins from hydrocarbon mixtures



July 1, 1947- F. J. soDAY 2,423,414 PROCESS FOR RECOVRING DITOLEFINS FROM HYDBOCA-RBOVN MIXTURES Filigdpril '7, l1943 s sheets-sheet 1 Ill' July 1, 1947- F. J. SODAY 2,423,414 PROCESS FOR RECOVERING DIOLEFINS FROM HYDROCARBON MIXTURES Filled April '7. 1943 5 Sheets-Sheet 2 #wam PROCESS FOR RECOVERING DIOLEFINS FROM HYDROCARBON MIXTURES Filed April 7, 1945 5 Sheets-513261.13

Patented July 1, 1947 PROCESS FOR RECO VERNG DIOLEFINS FROM HYDROCARBON MIXTURES Frank J. Soday, Baton Rouge, La., assigner to The United Gas Improvement Company, a corporation of Pennsylvania Application April 7, 1943, Serial No. 482,175

6 Claims. i

This invention `relates to the treatment of hydrocarbon mixtures containing both dioleflne hydrocarbons and olefine hydrocarbons for the separation of same.

More particularly, the invention relates -to a method for recovering diolene hydrocarbon material from `hydrocarbon mixtures containing in addition thereto other unsaturated hydrocarbon material such as one or .more monoolennes', and particularly one or more isoolenes.

It is an object of the invention to provide a process for treating a mixture of various unsaturated hydrocarbons, including diolene material and monoolene material, according to which process the diene material vmay be vrecovered in highly puried form and-in good yield.

Another object of Vmy invention is to provide a process by which a hydrocarbon mixture containing one or more aliphatic diolefines and one or more aliphatic mono-oleines, -particularly isoolei'ines, either with or without the Vpresence of one or more acetylenic hydrocarbons and/or one or more saturated aliphatic hydrocarobns, may be treated for the isolation of the particularly valuable aliphatic diolenne, or diolenes, in highly puriiied form.

A still further object of the invention is the provision of a method for separating isobutylene from liquids or gases containing the same in admixture with butadiene, with or without the presence of saturated aliphatic hydrocarbons and/or acetylenic hydrocarbons of generally similar boiling characteristics, vwhereby the relatively more valuable butadiene may be recovered in highly puried form for uses where a rened butadiene is necessary or desirable, such as for polymerization, either alone or with other hydrocarbons; as an intermediate in the production of other compounds; etc.

Further, another Aobject of the invention is the provision of a method for subjecting a hydrocarbon mixture containing substantial quantities of butadiene and isobutylene to a separatory treatment -for the recovery, on the one hand, of buta- -diene in relatively concentrated form, and the recovery, on the other hand, of isobutylene such as in the relatively more valuabledimeric-and/ or higher polymericform suitable for separate utilization as such, or for ,further conversion to still more lvaluable products.

vcarbon atoms per molecule of each of such consttuents. A

Various processes are known for the production of a combustible gas by methods wherein a petroleum oil, or a suitable fraction thereof, is Pyrolytically decomposed, such as, for example, in the vapor phase and with or without the aid of catalysts. As examples of such combustible gas may Lbe mentioned carburetted water gas and oil gas. The lgas resulting from processes of this nature, as well as higher boiling pyrolysis products resulting from cooling and/or condensing the gas, is rich in valuable resin-forming hydrocarbons including aliphatic diolefines, as well as in aliphatic mono-olefine hydrocarbons, the latter term including mono-,isooleiines Saturated aliphatic hydrocarbons are ,also generally present in considerable quantities, as may be certain cyclic and/or aromatic hydrocarbons of both saturated and unsaturated characteristics.

Besides the foregoing types of gases, other vgasmaking processes are capable of yielding valuable hydrocarbon mixtures to which my invention may likewise be applied. Thus, coal gas, coke oven gas, and refinery oil gas (such as is obtained as a by-product in the petroleum oil refining industry where hydrocarbon cracking conditions are generally so regulated as to produce liquid motor fuels as the major desired product) may if desired serve as `the source material for the hydrocarbon mixtures treated -in accordance with my present invention.

By a method or combination of methods which per se may be well AKnown in the art (e. g., absorption, adsorption, compression and/or refrigeration) it is comparatively easy to isolate a relatively narrow-boiling fraction from the combustible gas, said fraction comprising a mixture of saturated and unsaturated hydrocarbons preponderatingly of the same number of carbon atoms,

3 athough various hydrocarbons of a greater or lesser number of carbon atoms may be present in varying (although generally minor) degrees.

Thus, for illustration, a C4 fraction may be separated from combustible gas, which fraction may predominantly comprise various individual C4 hydrocarbons and relatively minor quantities of hydrocarbons oi greater and of lesser numbers of carbon atoms, the ratio of the C4 hydrocarbons to hydrocarbons other than C4s depending among other things upon the manner and conditions of separation thereof from the gas, as well as upon the original gas-making conditions.

Such a C4 fraction may contain butadiene, butene-l, butene-2, and isobutylene, as well as saturated hydrocarbons such as butane and isobutane and/or more unsaturated hydrocarbons such as vinylacetylene. Acetylenic hydrocarbons are generally present, if at all, in very minor proportions and the concentration thereof can be reduced to negligible values by known methods; and this is preferably, but not necessarily, done prior to applying the process of my present invention to the hydrocarbon mixture. The saturated hydrocarbons, while often present in very substantial proportions, may be readily separated from the remaining unsaturated hydrocarbons by known methods, for instance such as those depending upon the greater chemical reactivity of the `unsaturated hydrocarbons as compared with the chemical reactivity of the saturated hydrocarbons.

The remaining unsaturated hydrocarbons in the C4 fraction, comprising butadiene on the one hand and C4 mono-olene hydrocarbons on the other, are extremely difficult to satisfactorily separate into C4 mono-olenes and butadiene of Suniciently high purity and in suciently high yields. This is particularly true with respect to the separation of butadiene and isobutylene present inl such C4, fractions.

It-has already been proposed to separate butadiene irom its admixtures with butylenes (including the butenes, and in particular, isobutylene) by absorption with salts of heavy metals of groups IB and IIB of the periodic system, particularly monovalent salts of copper, mercury and/or silver, such as, for example, cuprous chloride, cuprous acetate, and similar salts, either dry or in solution and/or suspension in water, water containing ammonia, and the like; the separation depending in part at least upon the fact that while both the butadiene and the butylenes may be absorbed by the absorption medium, such as, for example, cuprous chloride, the resulting complexes have entirely different dissociation pressures, the butadiene-cuprous chloride complex having a dissociation pressure of only a few millimeters of mercury at room temperature, while the corresponding butylene-cuprous chloride complexes have dissociation pressures which may be as high as several atmospheres at the same temperatures, so that a selective absorption on cuprous chloride or the like salt may be obtained by a judicious choice of operating conditions. While this method may be employed when desired, and with the production of a satisfactory grade of butadiene for some purposes, it nevertheless leaves much to be desired in the way of costs of recovery and in yields, due in part at least to the fact that mono-olenes (and particularly isobutylene) which may be'present in admixture with the butadiene may likewise be absorbed to some extent by the cuprous chloride,

4 or similar absorbent, under the conditions favoring butadiene absorption.

While numerous attempts have been made to overcome the limitations imposed by the use of absorbing media such as cuprous chloride for recovering butadiene in highly puriiied form from admixture with butylenes, and particularly isobutylene, so far as I am aware no process heretofore proposed for the purpose is capable of substantially satisfying every important requirement, including particularly the following: reasonable costs, relatively high yields, high purity of the product butadiene; and simultaneous production of butylenes, especially isobutylene, in a form or forms which will be particularly valuable from the standpoint of separate utilization thereof, and the value of which can therefore be credited (at least in large part) to the butadiene recovery operation.

My invention is based upon the discovery that excellent results are obtained when the recovery of butadiene from hydrocarbon mixtures by means of cuprous chloride, or other monovalent salts of copper, mercury, and/or silver, either in the dry form, or in the form of a suspension and/or solution in Water, which may contain ammonia or the like, is combined with the conversion of the isobutylene of said hydrocarbon mixtures to dimers and/or higher polymers thereof.

Thus, by treatment of the hydrocarbon mixture containing butadiene and isobutylene, among other hydrocarbons, with a suitable catalyst, for example a mineral acid catalyst such as sulfuric or phosphoric acid, under suitable reaction conditions, most of the isobutylene present may be selectively converted to polymers of isobutylene, such as a material preponderating in diisobutylene, whereupon the remaining hydrocarbon mixture may thereafter readily be subjected to treatment with a selective absorption agent, such as cuprous chloride or cuprous acetate in solid or solution form, for the separation and recovery of butadiene in highly purified form.

The nal concentrating step preferably is carried out by contacting the partially concentrated material with either 1) finely divided dry cuprous chloride, suitably in a ball mill or similar reaction unit, (2) a slurry or suspension of cuprous chloride in water or other liquid, or (3) a solution of cuprous acetate in water containing ammonia, followed by stepwise desorption operations to isolate the butadiene present in pure form.

Alternatively, the hydrocarbon mixture may lf desired be first treated with an absorption agent, such as cuprous salts, after which one or more of the hydrocarbon concentrates produced thereby may be then subjected to the action of a catalyst under suitable reaction conditions adapted to selectively convert isobutylene present in the given hydrocarbon concentrate to dimers and/or higher polymers, the latter polymers then being separated from the hydrocarbon concentrate by any desired method, such as by distillation under reduced pressure, or otherwise.

The normally liquid polymers of isobutylene obtained by any of the foregoing steps, or their equivalent, will generally largely comprise di-isobutylene, which may be readily hydrogenated to iso-octane. The di-isobutylene, being readily convertible to this valuable anti-knock hydrocarbon, therefore constitutes an important by-product of the process. Tri-isobutylene, when present, may if desired be separated and employed i as 4a constituent .of imo'tor iuel, 'inasmuch .as it boils within the gasoline range. Higher polymers -of isobutylene', when present in Athe lreaction product, may be separated and .employed .as such, or otherwise utilized as desired.

In the description which follows, my invention will .be `described in connection with the Itreatment of an unsaturated C4 hydrocarbon fraction such Aas may -be separated by appropriate methods from a combustible gas produced by the vapor-phase pyrolysis `of petroleum oil, under temperature conditions of pyrolysis vvof above approximately v1100" F. and pressure conditions of approximately atmospheric, Aor slightly in -excess thereof, which Vpressure refers to the total pressure in the petroleum oil 'pyrolysis zone.

As illustrating a typical -isobutyleneand butadienecontaining unsaturated hydrocarbon `mixture of .the foregoing nature to which `my present invention may be readily applied with particularly desirable results, may be mentionedv a'crud-e unsaturated C4 hydrocarbon fraction separated from a combustible oil-gas `produced 4as indicated above and having the following roomposition `of -unsaturatesz .Table l Approximate B. P 'Content b y weight C. .Percent Butadiene -4. 7 50 isobutylene -'6. 7 28 `Butene-.l -6. 7 210 Butene-2 (Gis) +3. 7 r4 Butene-Z (Trans) +150 '3 Acetylene Hydrocarbons 1 C; and .C5 Hydrocarbons 4 In order to further illustrate vmy invention several embodiments thereof 'are described in lconnection with the accompanying drawings. It is to be understood vhowever Ythat this `is merely by way of added description, and Without intending thereby to in any Way limit my invention to the details mentioned. Other modications of -my invention will suggest Ythemselves to those skilled in the art upon becoming familiar with the present specification and claims.

In the drawings, Figure 1 is a ilow sheet set- -ting forth one preferred embodiment of the invention in which the step -of the selective polymerization of isobutylene is applied to the C4 hydrocarbon mixture prior to treatment thereof with -absorption agent for the separation of butadiene. A

Figure 2 illustrates the treatment of a Crhydrocarbon mixture containing butadiene and isobutylene with an absorption agent, such as one comprising cuprous salts, subjecting the reaction product or -solution to `stagewise deabsorption, and subjecting the hydrocarbon mixture from an intermediate deabsorption stage and containing substantial quantities of both butadiene and isobutylene to polymerization conditions selective as to the isobutylene.

Figure 3 shows a somewhat similar arrangement but in which the step of selectively polymerizing isobutylene is applied to the hydrocarbon mixture from the initial deabsorption stage and containing a preponderant portion of monoolenes, including isobutylene, but a relatively minor portion of diolenes, including butadiene.

Referring more particularly to Figure 1, the feed mixture comprising a 'C4 fraction containing butadiene :and isobutylene vmay tbe introduced "6 into polymerizing vessel 2 via :feed line 4. It may be introduced theretopreferably, but not necessarily, in 'the vapor phase for more eiective contact with the acid polymerization catalyst, and lconsequently heat-exchanger 6 may be provided in feed line 4 in case 4the 'C4 fraction is .charged to the system in liquid phase. Polymerizing vessel 2 may be provided with suitable packing of .conventional nature or otherwise, such Aas refractory pieces, or it may be relatively empty.

Mineral iacid polymerization catalyst, such as sulfuric acid, may be supplied to vessel 2 via line 8 and 4pump IU, the acid inlet being shown `for convenience as located at or near the bottom of vthe polymerizing vessel 2. If preferred for any reason, countercurrent contact between the 'C4 fraction and the acid catalyst agent might be employed, such as by admitting the acid at or near the top of the Ytower 2.

'By vsuitably vregulating the reaction conditions 'such as `temperature within the tower 'or vessel 2, .for instance .such as by circulating a suitable heating medium through a jacket (not shown) on said tower and/or `by suitably heating the acid catalyst outside tower 2, selective polymerization of a preponderant :portion of the butylenes, particularly isobutylene, may be caused to take place, the resulting polymerization product comprising largely diisobutylene with relatively minor lproportions of higher isobutylene lpolymers and/or other reaction products of the butylenes.

The butadiene, together with unreacted lbutylenes and any other residual hydrocarbons 'that may be present, may leave polymerizing vessel 2 via line I2, and be introduced 'into heat-exchanger vI4 and there subjected to condensation conditions. The condensed butadiene lfraction may leave heat exchanger I4 via line I5 which conducts it to tank I8 for storage preparatory to the second stage of the treatment. Tank I8 may thus act as a storage tank as well as a temporary surge tank between the process stages.

Returning to polymerizing vessel 2, acid catalyst containing isobutylene polymer may be withdrawn via line 20 and introduced into separator 22. This may be of any desired construction, and as shown includes a bafe arrangement disposed ina settling vessel of relatively large capacity which permits the separation of the acid catalyst and the isobutylene polymer such as .through simple layer formation.

Line 24 provided with pump 26 serves for the withdrawal of isobutylene polymer and any other separable material produced. This product `may be conveyed to storage, or to separation and/or further utilization, or otherwise, as desired.

Acid catalyst (saturated with hydrocarbon polymer) may be withdrawn from separator 22 and recycled to the polymerizing vessel 2 via line 8 Yand pump I0. Line 28 communicating with line 8 on the .inlet .Side of pump I0 may be provided for the introduction of makeup acid, as needed.

'Returning to the crude butadiene fraction 1in surge tank I8, this may be withdrawn via line 30 andgpassed into cooler 32 in'which'it is mixed With cuprous salt absorbing solution and/'or suspension coming Jfrom absorbent supply tank 34 via line 36 and pump 38.

The ymixture of cuprous salt absorb-ing solution and/or Suspension and crude butadiene frac- `tion 'may then be passed via line 46 and'pump 42 into absorber 44, which may be of any desired construction. For example, it may take the form of :a vessel of relatively Vlarge capacity provided with agitating means 46 and temperature control means 43 such as a coil withinA the tank for circulation of a fluid heating or cooling medium. Absorber 44 is preferably a vessel adapted to Withstand any superatmospheric pressure which it might be desired to impress upon the cuprous salt absorption portion of the system.

By suitably adjusting the temperature and pressure conditions obtaining in the absorption system, in conjunction with conditions of agitation and time of contact, particularly in absorber44, complexes of cuprous salt and butadiene are obtained Which are held in suspension and/or solution in the absorbing medium.

The absorbing medium containing this complex, lor mixture of complexes, may be removed from absorber 44 via line 58 and pump 52 and introduced into Vessel 54 for the separation and removal of monooleiine material, including Vany residual isobutylene. 1f desired, heat-exchanger 56 may be provided in line 5B to supply heat to the mixture of materials passing therethrough.

Vessel 54 is preferably constructed in a manner capable of withstanding considerable superatmospheric pressure.

By the application of heat, or by a reduction in pressure, or suitably by a combination of both of these methods, the material Contained in vessel 54 may be subjected to conditions sufficiently drastic to drive 01T in the form of vapor the butylenes, but insuiiiciently drastic to dissociate any substantial proportion of the cuprous chloride-butadiene complex.

The butylene, or butylenes, thus driven off in vapor phase may be removed via line 58 which if desired may conduct them to condenser 68. The condensed monoolene concentrate, suitably in liquid phase, may be removed from the system via line 62.

The cuprous salt absorption medium, partially stripped of mono-olefnes, may be Withdrawn from vessel 54 via line 64 and pump 88.

Line 68 communicates with line 64 on the outlet side 01 pump 86 and permits the recirculation of a portion of the absorption medium to vessel 54, if such should be desired for any reason.

The absorption medium from vessel 54 (less any portion thereof which might be recycled via line 68) may be introduced into a second Vessel l5 via line 64. If desired, heat-exchanger 12 may be provided in line 64 to supply heat to the material passing therethrough. Vessel 10, like vessel 54, is preferably constructed so as to be capable of withstanding considerable superatmospheric pressure.

By the further application of heat, or by a further reduction in pressure, or suitably by a combination of .both of these methods, the mixture contained in vessel 'Fil may be subjected to conditions suiiiciently drastic to drive off in the form of vapor substantially all the remaining butylenes. These conditions may be sufciently drastic to simultaneously dissociate an appreciable, although generally relatively minor, portion of the cuprous salt butadiene complex.

The butylene, or butylenes, thus driven off in vapor phase may be removed via, line 14. Since (as already indicated) an appreciable quantity of valuable butadiene may be present in the vaporphase eiuent from this intermediate stage of deabsorption, it may be economically desirable to recover same from admixture with the butylene or butenes.

For this purpose,line 14 may convey the gas mixture to condenser 'I6 Where it may be convertedinto a liquid unsaturated C4 hydrocarbon fraction and as such introduced into tank 18. From tank I8 it may be introduced intermittently or continuously, as desired, into the system as recycle stock, such as into admixture with the materials on their Way to absorber 44.

The cuprous salt absorption medium substantially completely stripped of butylenes and stripped to a relatively minor degree of butadiene, may be withdrawn from the second stage deabsorption vessel 'I8 via line 82 and pump 84.

Line 86 communicates with line 82 on the outlet side of pump 84 and permits the recirculation of a portion of the absorption medium to vessel it; if such should be desired for any reason.

The absorption medium from vessel 'I0 (less any portion thereof which might be recycled via line 86)v may be introduced into a third vessel 88 via line 82.V If desired, heat-exchanger 9U may be provided in line 82 to supply heat to the material passing therethrough.

Vessel 88 is also preferably constructed so as to be capable of withstanding a considerable superatmospheric pressure.

By the application of additional heat, or by a still further reduction in pressure, or suitably by a combination of both of these methods, the mixture contained in vessel 88 may be subjected to conditions sufficiently drastic to dissociate substantially al1 the remaining cuprous salt-butadiene complex and to drive off the resulting butadiene as a gas.

The butadiene thus driven oi in vapor phase may be removed via line 92 which if desired may conduct the butadiene vapor to condenser 94. The condensed butadiene concentrate, suitably in liquid phase, may be removed from the system via line 96. This product comprises butadiene of a relatively high degree of purity, which may be of the order of 98% or even higher.

rIhe cuprous salt absorption medium, substantially completely stripped of both butylenes and butadiene, may be Withdrawn from vessel 88 via line 98 and pump IDU.

If desired for any reason, a portion thereof may be recycled to vessel 88 by line IUI communicating with line 82.

The remaining absorption medium may be recycled to the process as shown.

In case dry cuprous salts, such as dry, finely divided cuprous chloride, is employed as the nal concentrating agent, the absorber 44 may comprise a ball mill or similar unit in which both absorption and desorption opertions are conducted. Desorbers 54, 78 and 88 may be eliminated. The process comprises essentially of contacting the hydrocarbon mixture with the dry cuprous chloride at low temperatures, followed by heating stagewise to remove unreacted material and finally decompose the butadiene cuprous chloride complex to liberate the butadiene present.

Referring more particularly to Figure 2, this represents diagrammatically a modification of Figure l wherein the crude unsaturated C4 hydrocarbon fraction is rst subjected to treatment with an absorption medium such as a cuprous salt solution in suspension, or dry cuprous salt such as cuprous chloride, and the absorbing medium containing unsaturated hydrocarbons absorbed therein is subjected to stagewise deabsorption in a manner similar to that already described, after which the eiiluent from the second stage of deabsorption (said effluent containing substantial quantities of butadiene and isobutylene) is subjected to the selective polymerization step for 9 selectively polymerizing butylenes, particularly isobuty-lene.

For convenience, like reference numerals have been applied to like elements and, for the sake of brevity, the description of the procedure in so far as it is similar will not be repeated.

The crude unsaturated C4 hydrocarbon fraction comprising the charge stock according to this modification is fed into the system via line 3B, and the operation of elements 30 to 14 and 82 to lill may be the same as that already described in connection with the correspondingly numbered elements of Figure 1.

It may be noted however that the quantities of butylenes, particularly isobutylene, in the respective eiuents from the iirst and second stages oi deabsorption of the cuprous salt solution or suspension may of course be substantially greater, due to the absence of the step of preliminarily selectively polymerizing isobutylene, present in the charge stock as was done in Figure 1.

The vapor phase eiiiuent from the second stage of deabsorption leaves vessel via line 14 and, instead of being condensed and recycled to the cuprous chloride absorption vessel 44 as in Figure 1, may be conducted directly into the acid catalyst polymerizing vessel 2. This eiiluent material in vapor phase contains considerable quantities of both butadiene and isobutylene, and may be subjected to selective polymerization conditions similar to those described in connection with Figure 1.

The operation of the selective polymerization unit 2 and associated equipment may be substantially the same as already described, and consequently need not be repeated. As a result of such operation, isobutylene polymer material may be withdrawn from the system via line 24 and pump 2B, while a butadiene concentrate may be withdrawn from tank I8 via line H0.

Heat-exchanger 6 in line 4 of Figure 1 is omitted from line 14 of Figure 2 since the effluent from vessel li! is already in the vapor phase. However, a heat-exchanger (not shown) may be provided in line 14 of Figure 2 if desired, and heating or cooling fluid circulated therethrough in a manner to adjust the temperature of the butadiene-butylene mixture flowing through line 14 to any desired value prior to introducing same into the polymerizing vessel 2.

As in Figure 1, the liquid phase cuprous salt concentrating process illustrated may be replaced by the dry cuprous chloride process, if desired, -by suitable vchanges in equipment.

Figure 3 illustrates a procedure closely related to that of Figure 2 except that the selective polymerization step is applied to the eiiiuent from the initial deabsorption step.

Here also, like reference numerals have been 'applied to like elements and, for the sake of brevity, the description of the procedure in so far as it is similar will not be repeated.

The crude unsaturated C4 hydrocarbon fraction comprising the charge stock according to this modication is fed into the system via line 3D, and the operation of elements 30 to 58 and 54 to lill may be the same as that already described in connection with the correspondingly numbered `elements of Figure 1.

As inthe case of Figure 2, it may be noted that the quantities of isobutylene, in the respective eiliuents from the iirst and second stages of deabsorption of the cuprous salt solution or suspension may of course be .substantially greater than is vthe case following theprocedure ofFigUle concentrating process 1, due to the absence of the step of preliminarily selectively polymerizing isobutylene, present in the charge stock.

The vapor phase eilluent from the initial stage of deabsorption leaves vessel 54 via line 58 and, instead of being condensed and removed from the system as oleiine concentrate as in Figure 1, may be conducted directly into the acid catalyst polymerizing vessel 2. This effluent material in vapor phase contains considerable quantities of butylenes, particularly isobutylene, but relatively little butadiene, due to the conditions of deabs-orption maintained in vessel 54. Consequently, the selective polymerization step conducted in polymerization unit 2 and associated equipment represents a convenient method of converting the isobutylene content of the rst stage eiiiuent into relatively more valuable liquid .polymers thereof.

'The operation of the selective polymerization unit 2 and associated equipment may be substantially the same as already described, and hence need not be repeated. As a result of such loperation, isobutylene polymer material may be Withdrawn from the system via line '24 and pump 26, while any residual butadiene and unconverted butenes may be withdrawn from tank IS via line IIB.

As in the case of Figure 2, heat-exchanger in line 4 of Figure 1 is omitted from line 58 of Figure 3 since the eiuent from vessel 54 is already in the vapor phase. Howeven. a heat-exchanger (not shown) may be provided in 'line 58 of Figure 3 if desired, and heating or cooling uid circulated therethrough in a manner to adjust the temperature of the butylene mixture (which may contain some butadiene) flowing through line 58 to any desired value prior to introducing same into the polymerizing vessel 2.

The second stage eiiuent (containing substantial quantities of both butadiene and butylenes, particularly isobutylene) may be condensed and recycled to the system such as at line 4U, as previously described in connection with Figure 1.

As in Figure 1, the liquid state cuprous salt illustrated may be replaced by the dry cuprous chloride process, if desired, by suitable changes in equipment.

Numerous modifications and variations of the foregoing procedures will become apparent to those skilled in the art from a consideration of the description herein.

rlhus, the procedures of Figures 2 and 3 might be combined; i. e., mer-ization step might be applied to each of the vapor phase eiliuents from both the initial and the second deabsorption stages of operation.

On the other hand, the procedure of Figure 1 might kbe combined with either the procedure of Figure `2 or the procedure of Figure 3; i. e., the selective catalytic polymerization step might be applied not only to the initial charge stock as in Figure 1 but also to either of the eiiluents from the second or the rst deabsorption stages as shown in Figure 2 or 3 (respectively) Or the procedure of all three gures might be combined; i. e., the selective catalytic polymerization step might be applied not only to the initial charge stock as in Figure 1 but also to the effluents from the first two deabsorption stages kas in Figures 2 and 3 combined.

While I have illustrated three stages of deabsorption ofthe cuprous salt absorption medium, obviously more stages Vmight vbe employed without departing from the spirit of my invention. It is also cuneeivable that only two stages of deabthe selective catalytic poly-V sorption might be desirable under certain circumstances.

Also, while the mineral acid selective polymerization step has been described as carried out with the hydrocarbon feed stock in the vapor phase, liquid phase polymerization conditions might be employed by suitably adjusting the temperature and pressure conditions obtaining in the polymerizing Vessel for that purpose.

Likewise, the treatment with the cuprous salt absorption medium has been described as carried out with the hydrocarbon feed stock in the liquid phase. On the other hand, by suitably adjusting the temperature and pressure conditions this portion of my procedure may be conducted with the hydrocarbon material in the vapor phase, if desired. The same applies to the dry cuprous chloride concentrating process.

In other words, any combination of liquid phase and/or vapor phase operations may be employed in practicing the component steps of my invention without departing from the spirit thereof.

The catalystemployed for the polymerization step may be any desired agent adapted to selectively convert butylenes, and particularly isobutylene, to polymer material in which the dimer preferably predominates, and in the presence of butadiene.

As such catalytic agents there may be employed l mineral acids such as sulfuric and phosphoric acids. Sulfuric acid having a concentration in the range of approximately 40 to 80%, and particularly in the range of 6075%, is very desirable for this purpose.

The polymerization temperatures are preferably correlated with the strength of acid employed and the composition of the hydrocarbon charge to the polymerization zone to yield the results described herein. Temperatures in the polymerization zone ranging from approximately 25 to 80 C. and more preferably in the range of 40 to 70 C., are suitable for the purpose.

As already indicated, the absorbing mediun employed preferably comprises a heavy metal salt capable of forming complexes or addition compounds with diolefines and monoolenes. Salts of heavy metals of groups 1b and 2b of the periodic system, especially salts of such metals in their monovalent form, are suitable. For example, cuprous, mercurous and silver salts are suitable. Cuprous halides, and especially cuprous chloride, are outstanding for my present purposes.

Salts of the type described may be employed in the dry state, or suspended in an inert organic solvent, or in an aqueous medium. When aqueous solutions are employed, it may be desirable to have present an excess of the solid salt so that the absorption medium is in effect a salt slurry.

Hydrcchloric acid and/or ammonium chloride may be present, if desired, to increase the solubility of the heavy metal salts in water. On the other hand, basic substances such as an ethanolamine (and particularly triethanolamine) or dissolved ammonia may be present in the metal salt absorption medium. Salts of alkali and alkaline earth metals (such as sodium chloride and calcium chloride) may likewise be present in the absorption medium. Amine salts might also be present.

Preferred absorbing systems are (1) cuprous acetate dissolved in dilute aqueous ammonia and (2) solid, dry cuprous chloride.

The pressure and temperature conditions obtaining in the absorption and dea'bsorption stages l material,

may be varied with considerable latitude, without departing from the spirit of the invention.

Generally speaking, superatmospheric pressures may be preferred throughout al1 or at least a part of the system, for at least two reasons, (a) the absorption of unsaturated hydrocarbon material in the absorber is thereby rendered relatively more complete, and (b) when deabsorbing under superatmospheric pressure conditions, the Vapor phase effluents from the deabsorption zone or zones may be condensed when necessary or desired by means'of ordinary surface or river water, Without the necessity for special refrigeration means.

As hereinbefore indicated, if acetylenic hydrocarbons are present in the mixture to be treated in accordance with my invention, it may be preferred to subject the initial charge stock to a preliminary treatment for the removal of the acetylenics. For example, treatment with basic cuprous salt solutions (such as an ammoniacal cuprous chloride solution) permits removal of the acetylenics in the form of insoluble cuprous acetylides. Other suitable methods for removing acetylenics include treatment with freshly prepared sodamide.

For the sake of simplicity, conventional apparatus elements such as valves, vents, traps, compressors, gauges, and other apparatus elements not essential to an understanding of the process, have not been shown 0n the drawings nor described, since these would be supplied as a matter of course by those skilled in the art practicing the present invention.

The process may be illustrated by means of the following example.

E ample A 50% light oil butadiene fraction having a composition similar to that described previously was continuously charged to a vertical reaction tower containing 65% sulfuric acid at a temperature of 55 C. The butadiene fraction was introduced into the lower portion of the tower by means of a fritted glass disc.

Approximately of the isobutylene present in the fraction was removed by this procedure, while less than 5% of the butadiene present was removed. `Approximately 2/3 of the isobutylene removed was iso-lated subsequently as diisobutylene, the remainder comprising triisobutylene, with smaller proportions of higher polymers.

Upon contacting the treated butadiene with dry, nely divided cuprous chloride in a ball mill at 15 C. followed by removing unreacted material at 15-50o C., then decomposing the butadiene-cuprous chloride complex at Gil- C., approximately 86% of the butadiene present is isolated as 98.5% butadiene.

While particular steps and procedures for separating dienes and monooleflnes, particularly isoolenes, have been described, it is to be understood that these are by way of illustration only. Therefore, changes, omissions, additions, substitutions and/or modications may be made within the scope of the claims without departing from the spirit of the invention.

I claim:

1. A process for the separation of diolene material from a mixture thereof with monoolene including isoolene material, which comprises contacting said mixture with an absorption medium under conditions of temperature and pressure such that both diolene material and monoolefine material, including monoisoolefine material, are absorbed therein; sub.- jecting said absorption medium containing absorbed.v material in a plurality oi deabsorption stages to increasingly drasticconditions oi deabsorption, thereby obtaining at least one iraction containing substantial quantities of both dioleiine material and monoolene material, including isooleiine material, and at least one fraction of relatively concentrated diolefine material, subjecting said. iirst-mentioned fraction containing substantial quantities of both diolefine material and monoolene material to selective polymerization conditions sufciently drastic to polymerize at least a preponderant portion of said monoolefine material', including` said isooleii-ne. material', but insuiiciently drastic to afiect a largeportion` of said diolefme material; and separating monooleiine polymerization products from the resulting mixture, the remaining portion oi said resulting mixture constituting additional relatively concentrated diolefine material.

2. A process for the separation of butadiene from admixture with C4 monoolene material, including isobutylene, which comprises contacting said mixture with an absorption medium under conditions of temperature and pressure such that both butadiene and isobutylene areA absorbed therein; subjecting said absorption medium containing absorbed material in a plurality oi deabsorption stages to increasingly drastic conditions of deabsorption, thereby obtaining at least one fraction containing substantial quantities of both butadiene and isobutylene, and at least one fraction of relatively concentrated butadiene; subjecting said first-mentioned fraction containing substantial quantities of both butadiene and isobutylene to selective polymerization conditions suiiiciently drastic to polymerize isobutylene to polymer including diisobutylene, but insuiciently drastic to aiect a large portion of said butadiene; and separating isobutylene polymer from the resulting mixture, the remaining portion of said resulting mixture constituting additional relatively concentrated butadiene.

3. A process for the separation of butadiene from a hydrocarbon mixture containing in admixture therewith butenes, including isobutylene, which comprises contacting said mixture with an absorption medium comprising a monovalent salt of a metal of the group consisting of copper, mercury and silver under conditions of temperature and pressure such that both butadiene and isobutylene are absorbed therein; subjecting said absorption medium containing absorbed material in a plurality of deabsorption stages to increasingly drastic conditions of deabsorption, thereby obtaining at least one fraction containing substantial quantities of both butadiene and isobutylene, and at least one fraction of relatively concentrated butadiene; subjecting said firstmentioned fraction containing substantial quantities of both butadiene and isobutylene to selective polymerization in the presence of a mineral acid catalyst and under conditions sufficiently drastic to polymerize isobutylene to polymer including diisobutylene, but insuiciently drastic to affect a large portion of said butadiene; and separating isobutylene polymer from the resulting mixture, the remaining portion of said resulting mixture constituting additional relatively concentrated butadiene.

4. A process for the separation of butadiene from a hydrocarbon mixture containing in admixture therewith butenes, including isobutylene,

comprising contacting said mixture With an an comprising cuprousl chloride sorption medium under conditions of temperature and pressure such that butadiene and isobutylene are absorbedv th'erein.; subjecting said absorption medium containing absorbed material in a plurality of doab-l sorption stages to increasingly drastic conditions oi deabso-rption, thereby obtaining at least one fraction containing substantial quantities of butadiene and isobutylene, and at least one fraction oi` relatively concentrated butadiene; subjecting said first-mentioned fraction containing substantial quantities of butadiene andv isobutylene to selective polymerization in the presence of sulfuric acid as catalyst under conditions sufficiently drastic to polymerize isobutylene to polymer including. diisobutylene, but insuiiiciently drastic to affect a` large portion of saidY butadiene; and separating isobutylene polymer from the resulting mixture, the remaining portion of said resulting mixture constituting additional relatively concentrated butadiene.

5. A process for the separation of butadiene from a, hydrocarbon mixture containing butadiene and butenes including isobutylene, comprising contacting said mixture with an absorption medium comprising a monovalent salt of copper under conditions of temperature and pressure such that butadiene and C4 monooleiine material, including isobutylene, are absorbed therein; subjecting said absorption medium containing absorbent material in at least three separation stages to increasingly drastic conditions of separation, thereby obtaining (a) at least one C4 monoolefine fraction relatively low in butadiene content (b) at least one fraction containing substantial quantities of butadiene and isobutylene, and (c) at least one fraction ci relatively concentrated butadiene; subjecting said fraction (b) containing substantial quantities of butadiene and isobutylene to selective polymerization in the presence of sulfuric acid as catalyst under conditions suiiiciently drastic to polymerize isobutylene to polymer including diisobutylene, but insufficiently drastic to aiect a large portion of said butadiene; and separating isobutylene polymer from the resulting mixture, the remaining portion of said resulting mixture constituting additional relatively concentrated butadiene.

6. A process for the separation of butadiene from a hydrocarbon mixture containing butadiene and butenes including isobutylene, comprising contacting said mixture with an absorption medium comprising a monovalent salt oi co-pper under conditions of temperature and pressure such that butadiene and C4 monoolene material, including isobutylene, are absorbed therein; subjecting said absorption medium 'containing absorbed material in at least three separation stages to increasingly drastic conditions of separation, thereby obtaining (a) at least one C`4 monoolenic fraction relatively low in butadiene content, and containing isobutylene, (b) at least one fraction containing substantial quantities of butadiene and C4 vmonooleflne material, including isobutylene, and (c) at least one fraction of relatively concentrated butadiene; subjecting said fraction (a) containing a substantial quantity of C4 monoolene material, including isobutylene, but relatively low in butadiene content to selective polymerization in the presence of sulfuric acid as catalyst under conditions sufiiciently drastic to polymerize isobutylene to polymer including diisobutylene; separating isobutylene polymer from the resulting mixture, the remain- 15 ing portion of said resulting mixture containing residual unsaturated C4 hydrocarbon material; and recycling said fraction (b) containing substantial quantities of butadiene and C4 monoolefine material to the cuprous salt-unsaturated hydrocarbon contacting zone for further separation of butadiene and C4 monoolene material contained in said fraction.

FRANK J. SODAY.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS Number Name Date 1,999,159 Van Peski Apr. 23, 1935 2,230,274 Soday Feb. 4, 1941 2,271,092 Perkins et al. Jan. 27, 1942 2,318,988 Craig May 11, 1943 2,322,281 Craig June 22, 1943 1,988,479 Brooks Jan. 22, 1935 v20 pages 19-29. Translation in 21, 1931, Reaction Velocity of Sulfuric Acid with Unsaturated Hydrocarbons. Reprint in 260- 683.15, 9 pages.

Lure et al., Sintet Kauchuk (1934), No. 6, 260-6815, 35 pages.

Hadns'worth et al., J. A. C. S. 43, 1 (1921). 

